1. Field of the Invention
The invention relates to an additive pack which comprises a water-soluble capsule and a water-dispersible polymer powder (dispersion powder), to the use of the additive pack in the production of aqueous mortars with mineral binders, and to aqueous mortar compositions obtained with the additive pack.
2. Description of the Related Art
Production of mortar compositions using mineral binders involves mixing mineral binders such as cement, gypsum, lime, or loam together with fillers such as sand, and with other additives such as dispersion powders and/or thickeners, and then mixing these with water to give the mortar compositions. In recent years the materials known as factory-produced dry mortars have been used successfully to produce these mortar compositions. These dry mortars are premixed in accordance with defined formulations at the factory of a producer of construction materials, and provided in packaged form (bagged product) or in bulk form as a silo product. Prior to use, the dry mortars are then simply mixed with a defined quantity of water.
The main constituents of these dry mortars are the mineral binder, such as cement, gypsum or lime, and the filler, for example sand. In order to improve the mechanical properties of the hardened mortar composition it is also possible to add additives such as dispersion powders, optionally thickeners to obtain a desired rheology, and also setting accelerator or setting retarders to obtain desired use properties. Examples of these dry mortars are found in EP 0 722 917 B1, EP 1 238 958 B1, and EP 2 537 818 A2.
Additives for dry mortars are known. By way of example, WO 03/106369 A1 describes an additive for improving flow properties which comprises cellulose ether and polycarboxylic acids. The patent EP 2 297 060 B1 describes a rheology additive made of dispersing agent and stabilizer. WO 2011/073224 A1 describes adhesion improvers which comprise plasticizers. WO 2011/098412 A1 describes a hydrophobizing agent.
The expression “water-dispersible polymer powders” (“dispersion powders”) is used for powder compositions which are accessible by means of drying of the corresponding aqueous polymer dispersions in the presence of protective colloids. By virtue of this production process, the fine-particle polymer resin of the dispersion becomes coated with a water-soluble protective colloid. During drying, the protective colloid particles act as a jacket which prevents caking of the polymer particles. On redispersion of the dispersible polymer powders in water, the protective colloid redissolves in water, and an aqueous dispersion of the original polymer particles is again obtained (Schulze J. in TIZ, No. 9, 1985).
The advantage of the dry mortar compositions discussed above is a uniform product quality by virtue of the standardized industrial production process. However, a precondition for supply of these dry mortar formulations to construction sites is a highly developed infrastructure for the transport of the dry mortars to the end user, involving not only silos but also distributors of construction materials or construction-industry markets. To the extent that the dry mortars, dispersion powders, or construction-chemistry additives are in solid form, they are generally marketed in a form packaged in bags or sacks made of paper or of plastics such as polyethylene or PVC. An example of the packaging used for dispersion powders or dry mortars is the multilayer packaging found in WO 2005/092724 A1.
Regions with less developed infrastructure generally have local access to the main materials for a mortar composition, i.e. cement, sand and water, but do not necessarily have access to ready-to-use dry mortar.
It would therefore be desirable to provide additives for improving the properties of mortars, and specifically in a supply form in which these can be combined with the main materials for aqueous mortar compositions, in order to obtain quality of construction materials that is comparable with that of materials produced with use of ready-to-use dry mortars. These additives should also be made available in a form in which they can immediately be used in the quantity required for mortar production, for example by virtue of packaging in a pack of appropriate size. Disadvantages such as dusting during opening of the packaging, and packaging waste, should be avoided here.